On the Weathering Mechanism of LD Converter Slag

Abstract

In order to elucidate the weathering mechanism of LD converter slags, the actual slags were exposed to air as well as water and autoclaved. The behaviors of disintegration, mineral phases and reaction products of slags were mineralogically examined. Various factors which affect disintegration were also discussed. Results obtained are as follows:
(1) LD slag mainly consists of five mineral phases, namely dicalcium silicate, tricalcium silicate, lime, wustite and dicalcium ferrite. Two types of lime in precipitating state are observed. One is a large cluster with the order of milimeter in size, and the other is a small dispersion with tens of micron.
(2) Disintegration of slag is closely related to the amount, distribution and characteristics of the lime phase in slag. The higher in free lime content, the more disintegration is, but when the slag contains less than 1% of free lime, it hardly disintegrates. Divalent oxides, FeO and MnO, dissolved in lime phase also restrain disintegration.
(3) The volume expansion by hydration of lime is a main cause of weathering and disintegration of slag. Silicates on surface also hydrate, but don't result in disintegration.
(4) Accordingly, to use steelmaking slag for raod and construction materials, an effect to decrease free lime in slag should be made.